The present invention relates to a pneumatic tire, more particularly to a motorcycle tire for running on rough terrain improved in the uneven wear resistance and cornering performance.
In general, motorcycle tires for running on rough terrain, designed for use in for example motocross race or off-road race, are provided in the tread portion with a plurality of independent blocks, for example as disclosed in JP-A-2007-326520, so that the tread blocks bite into the ground of rough terrain and provides improved off-road traction and cornering performance.
As shown in FIG. 6 for example, the tread blocks (b) of such a motorcycle tire (a) are provided with ground contacting surfaces (bs) whose profiles (contours) are an arc of a relatively small radius of curvature (rs) of about 50 to 70 mm in the meridian section of the tire including the tire rotational axis.
In such block (b), in comparison with the ground pressure in the central region (bc) of the ground contacting surface, the ground pressure at each axial edge (be) of the ground contacting surface becomes decreased. In particular, during cornering, the axial edges (be) of the axially outermost shoulder blocks (b1) do not function well and thereby the cornering performance can not be improved fully.
Further, as the shoulder blocks (b1) are subjected to large ground pressure during cornering, the amount of wear in the central region (bc) of the ground contacting surface becomes increased in comparison with the amount of wear at the axial edges (be). As a result, uneven wear is liable to occur in the vicinity of the axial edges (be),